Evaluation of the patch test results in pediatric patients between 1996-2017

Introduction & Objectives During the last three decades, positive patch test results and allergic contact dermatitis (ACD) in children have been increasingly reported worldwide. The exposure patterns with allergens differ depending on the individual and geographical variability. There is no evidence based, standardized patch test series in pediatric age group as in adults. Recently, there have been several attempts to create an standard allergen series for this age group. This study aimed to evaluate the patch test results in a relatively large group of pediatric patients in Turkey, to find out the frequency and relevance of the allergens giving positive reactions, to define the allergen sources causing sensitization and/or ACD, to evaluate the test results with special regard to the applied test series and recently suggested European pediatric allergen series and to suggest a special standardized patch test series for Turkish pediatric population. Materials & Methods In this retrospective, cross-sectional, single-center study, 317 pediatric patients aged 0-18 years with clinically suspected ACD, who were patch tested in the Allergy Outpatient Clinic of Istanbul Faculty of Medicine, Department of Dermatology and Venereology between 1996-2017, were reviewed. Patients' files were evaluated regarding demographic variables (age, sex, atopy), patch test results, and the relevant contact allergens. Current relevant reactions were further analyzed according to whether they were included in the standard series and the recently suggested patch test series of allergens. Results Among 317 patch tested patients, 146 (46.1%) had one or more positive reactions. The male:female ratio was 1:2.5. The age range was 1-18 years (median: 14 years). Personal history of atopy was present in 34.4% (n=109) of the patients. MOAHLFAP index in % was 28.4/4.7/21.8/46.1/0/30.3/0/46.1. Nickel sulphate was the most frequent sensitizer (68/317, 21.5%) showing concomitant positive reactions to palladium chloride (30/317, 9.5%) and/or cobalt chloride (5/317, 1.6%), followed by thimerosal (40/270, 14.8 %), p-phenylenediamine (21/251, 8.4%), ammoniated mercury (15/261, 5.7%), ammonium persulfate (7/22, 31.8%), chloromethylisothiazolinone/methylisothiazolinone (6/317, 1.9%), fragrance mix I (4/317, 1.3%), neomycin (4/317, 1.3%), colophony (3/317, 0.9%). Among 146 patients, ACD was diagnosed in 98 (67.1%) according to current clinical relevance of patch test reactions. The allergen with the highest rate of current clinical relevance was chloromethylisothiazolinone/methylisothiazolinone (n=6, 100%) in cosmetics followed by p-phenylenediamine (n=19, 90.5%) in black henna tattoos and hair dyes, ammonium persulfate (n=6, 85.7%) in hair bleaching products and nickel sulphate (n=39; 57.4%) in jewelry and clothing accessories. The current clinical relevance rate of ammoniated mercury in antiseptics used for umbilical cord and wound care was 40%. None of the patients developed ACD due to thimerosal, another mercury compound found mainly in vaccines, although it was found to be an indicator of mercury allergy due to its high rate of cross-reactivity with other mercury compounds. ACD was mainly localized on hands (n=33, 33.7%), followed by metal contact sites (n=32, 32.7%), face (n=24, 24.5%) and contact areas of topical drugs (n=15, 15.3%). Occupational ACD was diagnosed in 15 patients (4.7%). Most of them were hairdresser apprentices (n=13) with relevant sensitizations mainly to p-phenylendiamine (n=11) and ammonium persulfate (n=6). ACD would be diagnosed in almost ¾ of the patients (73.5%) by testing with the European baseline (standard) series only, while ¼ of the patients would have been missed without testing with the additional allergen series and patients' own products. Moreover, the diagnosis of ACD could only be established by testing with patients' own products in 11.2% of the cases. The suggested European pediatric standard series and additionally suggested allergens could identify ACD in 63.2% of the patients. Almost one third of the patients (28.6%) would have been missed by testing with these suggested allergens only. Conclusions In the light of our findings, we would recommend to include nickel sulphate, chloromethylisothiazolinone/methylisothiazolinone, fragrance mix I and II, neomycin, and colophony in the standard Turkish pediatric patch test series. We also propose the inclusion of thimerosal as an indicator for mercury allergy which is frequent in our country. p-Phenylenediamine, ammoniated mercury, nitrofurazone, polyethylene glycol, ammonium persulfate and toluenesulfonamide formaldehyde resin should be placed in the additional allergen series to be tested only in suspicious cases. In certain cases, testing with patients' own products is also essential to make a correct diagnosis of ACD.